I have the same with my elementary school:
24 Dec. - 6 Feb. Winter Vacation
7 Feb. - 16 Feb. Return to school, 6th graders graduate, teacher's party.
17 Feb. - 1 Mar. Spring break
2 March - New School Year starts
My co-teacher told me that winter vacation is a just that, Vacation. For the last week most teachers come to work for a few days to prepare for their students leaving. Then, school is in session for a week to finish up a few lessons and say goodbye. Spring break is when teachers prepare for their new students.